JP2008270632A - Testing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a testing apparatus and method whereby the defects of a conductive pattern can be sensed with a high accuracy. <P>SOLUTION: In the testing apparatus and method, a sample having conductive patterns 10 is scanned by an electron beam 20 while the irradiating position of the electron beam 20 is vibrated by a predetermined amplitude when irradiating each conductive pattern 10 by the electron beam 20. Such an electric signal as absorbing currents generated by the irradiation in each conductive pattern 10 and as the voltages caused by the absorbing currents is sensed by using probes 31, 32 and amplifiers. Then, the varying amounts of the electric signals, which are sensed among the respective vibrations when scanning each conductive pattern by the electron beam 20, are so searched as to sense the defect of each conductive pattern 10 from the difference between the varying amounts obtained when such a defect as a high-resistance via 12a exits in the region of the vibration and obtained when the defect does not exist. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inspection apparatus and an inspection method, and more particularly to an inspection apparatus and an inspection method used for defect inspection of wirings and the like formed in a semiconductor device.

  In developing and manufacturing various semiconductor devices such as LSI (Large Scale Integration), a technique called defect analysis is generally employed to improve performance and yield. This is a technique for improving the manufacturing process by identifying the position of a defect that has unexpectedly occurred in the manufacturing process of a semiconductor device, analyzing it, and elucidating the cause of the occurrence of the defect. Such a technique is regarded as a very important technique in developing a process for manufacturing a high-performance and high-quality semiconductor device.

  By the way, with the miniaturization and high integration of semiconductor devices, conductive patterns such as wirings and vias as well as transistors have become finer, and the density thereof has been increasing. Therefore, it is becoming difficult to inspect defects of such a conductive pattern, particularly to identify the defective portion. For example, as in IR-OBIRCH (Infrared-Optical Beam Induced Resistance CHange) analysis, a method for optically identifying a defective portion is not suitable for a high-density pattern having a spatial resolution of about 1 μm or less unless special measures are taken. There is a limit to application.

Therefore, in recent years, a scanning electron microscope (SEM) is used to irradiate a sample on which a conductive pattern such as a wiring is formed while scanning a charged beam such as an electron beam, and the absorption generated in the conductive pattern. A method for identifying a defective portion of the conductive pattern by detecting a current has been proposed (see, for example, Patent Documents 1 and 2). Furthermore, an attempt has been made to improve the detection sensitivity (S / N ratio) by applying intensity modulation or pulse modulation to the irradiating electron beam and detecting an absorption current synchronized with the modulation (for example, patent document). 3 and 4). In addition, a method for identifying a defective portion of a conductive pattern by detecting a voltage generated in the conductive pattern due to an absorbed current has been proposed (see, for example, Patent Document 5).
JP 2002-343843 A JP 2002-368049 A Japanese Patent Application Laid-Open No. 2004-296771 Japanese Patent Laid-Open No. 2005-71775 JP 2006-105960 A

  In the case of a method for identifying a defective portion of a conductive pattern by irradiating the sample while scanning with an electron beam and detecting an electric signal such as an absorption current generated in the conductive pattern or a voltage generated thereby, When an electron beam is irradiated onto a normal conductive pattern without defects during scanning, the detected electrical signal gradually changes as the irradiation position moves.

  Here, for example, when a resistive defect exists in the middle of the conductive pattern, when the electron beam is irradiated while scanning, the defect is detected when the electron beam is irradiated. The electric signal shows a change different from that when the normal part of the conductive pattern is irradiated with the electron beam. Until now, the defective part of the conductive pattern was specified based on the change of such an electric signal.

  However, when the resistance of the defect is not so large, the electrical signal detected when the electron beam is irradiated to such a defective portion is the electric signal when the electron beam is irradiated to the normal part. It is difficult to identify the defective part.

Therefore, a method capable of detecting a defect with higher accuracy is desired.
The present invention has been made in view of such a point, and an object thereof is to provide an inspection apparatus and an inspection method capable of performing defect inspection with high accuracy.

  In the present invention, in order to solve the above problems, in an inspection apparatus for inspecting a sample, means for irradiating the sample with a charged beam, and scanning the charged beam to be irradiated while vibrating the irradiation position with a constant amplitude There is provided an inspection apparatus characterized by comprising: means for causing an electric signal generated in the sample by irradiation of the charged beam.

  According to such an inspection apparatus, the charged beam is scanned over the sample while vibrating the irradiation position with a constant amplitude, and an electric signal generated in the sample by the irradiation is detected. Thereby, it becomes possible to detect an electric signal while the irradiation position of the charged beam vibrates with a constant amplitude.

  Therefore, for example, the amount of change in the electrical signal detected during each vibration during charged beam scanning is obtained, and based on the difference in the amount of change when there is a defect in the vibration region, Sample defects can be detected.

  According to the present invention, in order to solve the above-described problem, in the inspection method for inspecting a sample, the charged beam is scanned and irradiated to the sample while vibrating the irradiation position with a constant amplitude. There is provided an inspection method characterized by detecting an electrical signal generated in the sample by irradiation.

  According to such an inspection method, the charged beam is scanned over the sample while vibrating the irradiation position with a constant amplitude, and an electric signal generated in the sample by the irradiation is detected. Thereby, it becomes possible to detect an electric signal while the irradiation position of the charged beam vibrates with a constant amplitude.

  In the present invention, when irradiating a charged beam to a sample, the irradiation position is scanned while vibrating with a constant amplitude, and an electric signal generated in the sample by the irradiation is detected. As a result, it is possible to detect an abnormal portion of the sample with high accuracy, and to increase the accuracy of the inspection of the sample.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the inspection principle will be described.
1A and 1B are explanatory views of the inspection principle, in which FIG. 1A schematically shows the state of electron beam irradiation on a conductive pattern, and FIG. 1B shows the electron beam irradiation position of the conductive pattern and the amount of change in amplifier output. It is a figure which shows a relationship typically.

  Here, as a sample to be inspected, a sample having conductive patterns 10 in which upper and lower wirings 11 are alternately connected by vias 12 as shown in FIG. 1A is used, and an electron beam 20 is applied to such a sample. The case of irradiating is described as an example. In FIG. 1A, illustration of the interlayer insulating film and the like around the wiring 11 and the via 12 is omitted.

  When the electron beam 20 is irradiated, secondary electrons are generated from the irradiation position, and a part of the electron beam 20 that has not become secondary electrons is absorbed by the conductive pattern 10 in the region. A current, that is, an absorption current flows in the conductive pattern 10.

  Probes 31 and 32 are connected to the conductive pattern 10 at two locations. For example, when detecting an absorption current generated in the conductive pattern 10 when the electron beam 20 is irradiated, the two probes 31 and 32 are each connected to a current amplifier. The absorption current generated at the irradiation position of the electron beam 20 on the conductive pattern 10 flows through the conductive pattern 10 (the wiring 11 and the via 12) and is detected by the probes 31 and 32. Depending on the ease of flow in the conductive pattern 10 (for example, the presence or absence of a resistive defect as will be described later), the absorbed current is diverted from either one of the probes 31 and 32 or from both the probes 31 and 32. Detected.

  When detecting the voltage generated in the conductive pattern 10 due to the absorption current generated when the electron beam 20 is irradiated, one of the two probes 31 and 32 is grounded, and the other The probe 32 is connected to a voltage amplifier. When the electron beam 20 is irradiated and an absorption current is generated in the conductive pattern 10, the absorption current flows mainly to one of the grounded probes 31, and the length of the conductive pattern 10 from the ground point to the irradiation position of the electron beam 20. A voltage drop of a magnitude corresponding to the height occurs. The voltage is detected by the other probe 32. Further, the absorption current of the conductive pattern 10 at that time can be obtained from the detected voltage and the irradiation position of the electron beam 20.

  The absorption current of the conductive pattern generated by the electron beam irradiation is on the order of nA, and when detecting the absorption current and the voltage resulting from the absorption current, amplification by a current amplifier or a voltage amplifier is usually performed in this way. In this case, a signal (amplifier output) obtained by amplifying the absorption current detection value (detection current or detection voltage) detected by the probes 31 and 32 becomes the detection value (detection current or detection voltage) of the absorption current.

  Here, among the vias 12 of the conductive pattern 10, the vias 12 a at a certain part have a higher resistance than the other vias 12 due to some reason such as contamination of impurities, generation of voids, poor connection with the wiring 11, and the like. Assume that By irradiating the sample having the conductive pattern 10 with the electron beam 20, a resistive defect such as the via 12a is detected.

  In that case, in addition to the operation of scanning the electron beam 20 in one direction from the one probe 31 side to the other probe 32 side of the conductive pattern 10, the irradiation position of the electron beam 20 is fixed in parallel to the scanning direction. Vibrate (position modulation) with amplitude. That is, the electron beam 20 is scanned from one probe 31 side to the other probe 32 side of the conductive pattern 10 while vibrating the irradiation position with a constant amplitude. Then, the amount of change in the amplifier output of the absorption current and voltage obtained during each vibration during the scanning is detected.

  Here, FIG. 2 is an explanatory diagram in the case of scanning without vibrating the electron beam, (A) is a diagram schematically showing the state of electron beam irradiation to the conductive pattern, and (B) is a diagram of the conductive pattern. It is a figure which shows typically the relationship between an electron beam irradiation position and amplifier output.

  For example, when detecting an absorption current generated in the conductive pattern 10 when the electron beam 20 is irradiated, as shown in FIG. 2A, one of the conductive patterns 10 is not vibrated without vibrating the electron beam 20. Scan in one direction from the probe 31 side to the other probe 32 side. At this time, as shown in FIG. 2B, the amplifier output of the absorption current of the conductive pattern 10 increases as scanning progresses, but changes stepwise at the location of the high-resistance via 12a.

  Further, for example, when detecting the voltage of the conductive pattern 10 due to the absorption current generated when the electron beam 20 is irradiated, the electron beam 20 is not vibrated as shown in FIG. Then, the conductive pattern 10 is scanned in one direction from the one probe 31 side to the other probe 32 side. At this time, the amplifier output of the voltage on the probe 32 side increases as scanning progresses as shown in FIG. 2B, similar to the amplifier output of the absorption current, but at the location of the high resistance via 12a. It changes like a staircase.

  In contrast, when the electron beam 20 is scanned from one probe 31 side to the other probe 32 side of the conductive pattern 10 while vibrating, as shown in FIG. The amplifier output changes so as to vibrate according to the vibration of the irradiation position of the electron beam 20. When the change amount of the amplifier output in each vibration is expressed as a function of the irradiation position of the electron beam 20, it is as shown in FIG.

  That is, when the irradiation position of the electron beam 20 is vibrated in a normal portion of the conductive pattern 10 composed of the wiring 11 and the via 12 indicating normal resistance, the amplifier output obtained during the vibration is constant. Make a difference. Therefore, the amount of change in the amplifier output in the normal portion of the conductive pattern 10 becomes a constant value with respect to the irradiation position of the electron beam 20, as shown in FIG.

  On the other hand, when the irradiation position of the electron beam 20 is vibrated and the high-resistance via 12a is included in the vibration region, the amplifier output obtained during the vibration is a normal part of the conductive pattern 10. Compared with when the electron beam 20 is irradiated, the difference becomes larger.

  Accordingly, the amount of change in the amplifier output when the irradiation electron beam 20 is scanned while being oscillated is higher at the location of the high resistance via 12a than the irradiation position of the electron beam 20, as shown in FIG. It becomes convex and shows a constant value in other places. In addition, when the irradiation region of the electron beam 20 for one vibration is in the region where the via 12a showing high resistance is formed, the amount of change in the amplifier output during the vibration shows a constant value.

  When the amplifier output change amount having the relationship as shown in FIG. 1B with respect to the irradiation position of the electron beam 20 is displayed as a bright and dark image, for example, a bright portion (bright spot) at a location corresponding to the high resistance via 12a. ) Exists, and an image in which other areas are darker can be obtained. This bright spot can be easily visually recognized by appropriately adjusting a luminance offset, a dynamic range, or the like when displaying an image. The light / dark relationship may be reversed. That is, the same effect can be obtained even if an image in which a dark portion (dark spot) exists at a location corresponding to the high-resistance via 12a and the other regions become brighter is obtained.

  As described above, when the irradiation position of the electron beam 20 is not vibrated, the amplifier output has a relationship as shown in FIG. When such an amplifier output is displayed as a light and dark image as it is, for example, the brightness or darkness is gradually increased corresponding to the scanning direction of the electron beam 20 (increase direction of the irradiation position of the electron beam 20). An image is obtained. Of the amplifier output, the image of the portion that changes stepwise at the location of the high-resistance via 12a exists in the region where the brightness and the like gradually change. However, it is very difficult to extract a stepwise luminance change corresponding to the location of the high resistance via 12a from the region where the brightness and the like gradually change.

  The electron beam 20 is scanned while oscillating its irradiation position, the amount of change in the amplifier output obtained during each oscillation is detected, and this is imaged so that a defective portion such as the via 12a is bright or dark. By displaying as a point, it becomes possible to easily and accurately specify a defective part from the position of the bright spot or the like of the image.

  When performing defect inspection in this way, the detection resolution of a defective portion can be increased as the amplitude when the irradiation position of the electron beam 20 is vibrated is reduced. However, on the other hand, the smaller the amplitude is, the smaller the amount of change in the amplifier output at the defective portion becomes, so that it becomes difficult to detect such amount of change in the amplifier output. In setting the amplitude, the size of the wiring 11 and the vias 12 and 12a of the conductive pattern 10, the detection resolution of the defective portion, the detection limit of the amount of change in the amplifier output, the required characteristics of the device to be formed, and the like are taken into consideration. Set.

  By the way, the absorption current is very small on the order of nA. Therefore, when measuring such absorption current and the voltage resulting from it, noise that may exist in the measurement system is included in the amplifier output and the amount of change in the amplifier output. It is desirable to suppress the effect as much as possible.

  In order to suppress the influence of such noise, the following method can be used. That is, when scanning the electron beam 20 while oscillating the irradiation position, the irradiation position is changed with a constant amplitude, frequency, and phase, and the amplifier output having the same frequency and phase is phase-synchronized with a lock-in amplifier or the like. Detect using an amplifier. Furthermore, using such a phase-locked amplifier, the amount of change in the amplifier output is detected from the amplitude of the amplifier output detected when the irradiation position of the electron beam 20 is changed with a constant amplitude, frequency, and phase. As a result, it is possible to detect the amplifier output and the amplifier output change amount in which the influence of noise is suppressed, and it is possible to improve the accuracy of defect inspection.

  In the above description, the inspection principle is described by taking as an example the case where a defect exists in the via 12. However, of course, even when a defect exists in the wiring 11, it can be inspected based on the same principle. Is possible.

Next, an embodiment to which the above principle is applied will be described.
First, the first embodiment will be described.
FIG. 3 is a diagram illustrating a configuration example of the inspection apparatus according to the first embodiment.

  The inspection apparatus 60 of the first embodiment shown in FIG. 3 includes a sample chamber 61 in which a sample 40 such as a wafer on which a conductive pattern 40a is formed is set on a predetermined stage 61e, and a sample 40 set in the sample chamber 61. Is provided with an electron beam irradiation unit 62 for irradiating the electron beam 50 to the electron beam 50. Such a configuration is realized using, for example, an SEM.

  Probe 61a, 61b, 61c, 61d is provided in sample room 61 of this inspection device 60, and a pair of probes 61a, 61b or probes 61c, 61d are connected to one conductive pattern 40a, respectively. As shown in FIG. 3, of the pair of probes 61 a and 61 b, one probe 61 a is grounded, and the other probe 61 b is connected to the voltage amplifier 63. In addition, although illustration is abbreviate | omitted here, also about another pair of probes 61c and 61d, one side is similarly earth | grounded and the other is connected to the voltage amplifier 63 here.

  The electron beam irradiation unit 62 is provided with deflection electrodes 62a, 62b, 62c, and 62d for deflecting and irradiating the electron beam 50 in a predetermined direction, and lenses 62e and 62f.

  On the pair of deflection electrodes 62a and 62b side, after a scanning signal (X direction scanning signal) for scanning the electron beam 50 in the X direction with respect to the sample 40 is amplified by an amplifier or the like (not shown), for example. , Is supposed to be entered. On the other pair of deflection electrodes 62c and 62d, a scanning signal (Y-direction scanning signal) for scanning the electron beam 50 in the Y direction with respect to the sample 40 is amplified by, for example, an amplifier (not shown). It will be input later.

  At that time, the X-direction scanning signal is superposed with an oscillation signal controlled to have a predetermined amplitude, frequency, and phase, and the X-direction scanning signal after such superposition is amplified by an amplifier or the like, for example, as a deflection electrode. 62a and 62b are input. Thereby, the electron beam 50 is scanned in the X direction on the sample 40 while vibrating with a predetermined amplitude, frequency and phase.

  The scanning signals and oscillation signals in the X and Y directions used for scanning the electron beam 50 are set for the inspection apparatus 60 automatically, for example, by the computer 65 or manually by the operator using the computer 65. Is done. Data relating to these signals is stored in a storage device such as an HDD (Hard Disk Drive) provided in the computer 65, for example.

Details of scanning of the electron beam 50 using these scanning signals and oscillation signals will be described later.
Further, a part of the oscillation signal is also input to a lock-in amplifier 64 that is a phase-locked amplifier. When the electron beam 50 is scanned while oscillating according to the oscillation signal, a voltage signal that changes so as to oscillate according to the oscillation of the irradiation position of the electron beam 50 is detected using the probes 61a and 61b. A voltage signal (amplifier output) amplified by the voltage amplifier 63 is input to the lock-in amplifier 64.

  The lock-in amplifier 64 has a function of detecting an amplifier output synchronized with the oscillation frequency and phase of the oscillation signal among the amplifier outputs of the voltage amplifier 63 using the input oscillation signal. Further, the lock-in amplifier 64 uses an amplifier output obtained during each vibration at the time of scanning of the electron beam 50, and the amount of change in the amplifier output during each vibration at the time of scanning is determined from the magnitude of the amplitude. It has a function to detect.

  The amplifier output and the amount of change in the amplifier output detected by the lock-in amplifier 64 are input to a computer 65 having a predetermined image processing function. The output from the lock-in amplifier 64 is stored in a storage device such as an HDD provided in the computer 65. The computer 65 arranges the output from the lock-in amplifier 64 using the X-direction scanning signal and the Y-direction scanning signal, images it, and displays it on a display device 66 such as a display. .

  The computer 65 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD, an image processing unit, an input I / F (Interface), and the like. Are connected via a bus. The CPU executes processing using a program stored in the HDD, data relating to a scanning signal, data such as an amplifier output and an amplifier output change amount. The ROM stores basic programs and data executed by the CPU. The RAM stores programs and data being executed by the CPU. The HDD stores an OS (Operation System) executed by the CPU, application programs, and data. A display device 66 is connected to the image processing unit, and the image processing unit displays an image on the screen of the display device 66 in accordance with a drawing command from the CPU. A mouse and a keyboard are connected to the input I / F, and information input by the operator is received by these and transmitted to the CPU via the bus.

  In such an inspection apparatus 60, when the electron beam 50 is scanned and irradiated on the sample 40 while vibrating in a predetermined direction with a predetermined amplitude, frequency, and phase, an absorption current is generated in the conductive pattern 40a. To do. The probe 61b connected to the conductive pattern 40a detects a voltage signal caused by the absorption current that changes so as to vibrate according to the vibration of the irradiation position of the electron beam 50. The voltage signal is amplified by the voltage amplifier 63, and the amplified voltage signal (amplifier output) is input to the lock-in amplifier 64.

  The lock-in amplifier 64 detects an amplifier output having the same frequency and phase as the oscillation signal from the input amplifier output. Further, the lock-in amplifier 64 uses the amplifier output obtained during each vibration at the time of scanning of the electron beam 50, and detects the amount of change in the amplifier output during each vibration at the time of scanning from the magnitude of the amplitude. Is done. The amplifier output and the amplifier output variation detected by the lock-in amplifier 64 are output to the computer 65. The computer 65 arranges the amount of change in the amplifier output using the scanning signal of the electron beam 50, appropriately adjusts the offset, the dynamic range, etc., and displays it as an image on the display device 66.

  When there is a defect in the conductive pattern 40a of the sample 40, a position where the electron beam 50 is irradiated to the defective portion between the irradiation position of the electron beam 50 and the amplifier output change amount according to the example of FIG. Thus, a relationship is obtained in which the amount of change in the amplifier output changes so as to protrude. In the image of the display device 66, bright spots or dark spots are displayed at positions corresponding to such defective portions. Therefore, the operator of the inspection apparatus 60 can check the presence or absence of such a luminescent spot from the image of the display device 66 and grasp the presence or absence of a defect. In some cases, it is possible to identify a defective portion of the conductive pattern 40a based on the position.

  In addition, when the defect inspection of the sample 40 is performed in this way and the defect is detected and the location is specified, the cross section including the defect location is further focused on a focused ion beam (FIB). Etc., and the cross section thereof may be observed with an SEM, a transmission electron microscope (TEM) or the like, and the state of the defect portion may be grasped from the image.

Next, the scanning method of the electron beam 50 in the inspection apparatus 60 will be described in detail.
In order to perform scanning while vibrating the electron beam 50 as described above, for example, a scanning signal generating mechanism as shown in FIG.

FIG. 4 is a diagram illustrating a configuration example of the scanning signal generation mechanism.
The deflection electrodes 62a, 62b, 62c, and 62d are arranged so as to surround the irradiation path of the electron beam 50 when viewed in the irradiation direction of the electron beam 50, for example, as shown in FIG. At this time, the pair of deflection electrodes 62a and 62b for controlling the scanning of the electron beam 50 in the X direction are arranged to face each other with the irradiation path of the electron beam 50 interposed therebetween, and similarly controls the scanning of the electron beam 50 in the Y direction. The other pair of deflection electrodes 62c and 62d are also arranged to face each other across the irradiation path of the electron beam 50.

  In the example of FIG. 4, the output (voltage signal) of the X-direction scanning signal generation unit 71 that generates the X-direction scanning signal is supplied to the voltage amplifier 72 in one of the pair of deflection electrodes 62a and 62b. And the other deflection electrode 62b is grounded. Similarly, the output (voltage signal) of the Y-direction scanning signal generating unit 73 that generates the Y-direction scanning signal is input to one of the other deflection electrodes 62c and 62d via the voltage amplifier 74. The other deflection electrode 62d is grounded.

  The X direction scanning signal generation unit 71 and the Y direction scanning signal generation unit 73 that generate the X direction scanning signal and the Y direction scanning signal, respectively, can be configured to be included in the computer 65. The X-direction scanning signal generation unit 71 and the Y-direction scanning signal generation unit 73 are configured by providing a signal generator or the like that can set the content of the generated scanning signal using the computer 65 outside the computer 65. You can also

  Further, the output of the oscillation signal generation unit 75 that generates an oscillation signal can be input between the X direction scanning signal generation unit 71 and the voltage amplifier 72 (P point). The output is amplified by the voltage amplifier 72 after the output of the oscillation signal generator 75 is superimposed, and is input to the deflection electrode 62a.

  The oscillation signal generation unit 75 that generates the oscillation signal may be configured to be included in the computer 65, or a configuration in which an oscillator that can set the contents of the oscillation signal using the computer 65 is provided outside the computer 65. It is good.

Here, output examples of the X direction scanning signal generation unit 71, the Y direction scanning signal generation unit 73, and the oscillation signal generation unit 75 will be described.
FIG. 5 is a diagram illustrating an output example of the X-direction scanning signal generation unit, and FIG. 6 is a diagram illustrating an output example of the Y-direction scanning signal generation unit. 7A and 7B are diagrams illustrating examples of outputs from the X-direction scanning signal generation unit and the oscillation signal generation unit, in which FIG. 7A is an output example of the X-direction scanning signal generation unit, and FIG. 7B is an oscillation signal generation unit. Is an output example.

  For example, as shown in FIG. 5, the output of the X-direction scanning signal generation unit 71 monotonously increases from the output value Q1 (for example, voltage 0 V) to the output value Q2 at a constant rate during a certain time t1 to t2. It changes so as to decrease again to the output value Q1 at time t2. In the example of FIG. 5, the output of the X-direction scanning signal generation unit 71 is changed in the same manner as during the time t1 to t2 during the subsequent times t2 to t3, t3 to t4, and t4 to t5.

  For example, as shown in FIG. 6, the output of the Y-direction scanning signal generation unit 73 is constant at an output value R1 (for example, a voltage of 0 V) between certain times t1 and t2. In the example of FIG. 6, the output values R2, R3, and R4 are constant between the subsequent times t2 to t3, t3 to t4, and t4 to t5, respectively, and the output of the Y-direction scanning signal generator 73 as a whole is stepped. To change.

When only the outputs of the X-direction scanning signal generator 71 and the Y-direction scanning signal generator 73 as shown in FIGS. 5 and 6 are used, the electron beam 50 is scanned as follows.
That is, at time t1 to t2, the output of the X-direction scanning signal generator 71 is changed from the output values Q1 to Q2 while the output of the Y-direction scanning signal generator 73 is kept constant at the output value R1. Thereby, the electron beam 50 is scanned from one region to another region of the sample 40 as shown in FIG. At subsequent times t2 to t3, the output of the Y-direction scanning signal generator 73 is changed from the output value R1 to R2, the irradiation region of the electron beam 50 is moved in the Y direction, and the X value is scanned while the output value R2 remains constant. The output of the signal generation unit 71 is changed from the output value Q1 to Q2. Thereby, the electron beam 50 is scanned from the irradiation area after moving in the Y direction to a further area. The same applies to the times t3 to t4 and t4 to t5.

  On the other hand, in the first embodiment, the output of the oscillation signal generator 75 is superimposed on the output of the X-direction scanning signal generator 71. At this time, the output of the oscillation signal generation unit 75 has a predetermined amplitude, taking into account the accuracy of identifying the defective portion, the detection limit of the amount of change in the signal output from the conductive pattern 40a of the sample 40 by irradiation with the electron beam 50, and the like. Set to frequency and phase.

  The output at point P in FIG. 4 is, for example, the output of the X-direction scanning signal generator 71 as shown in FIG. 7A and the output of the oscillation signal generator 75 as shown in FIG. The superimposed value is amplified by the voltage amplifier 72 and input to the deflection electrode 62a. Thereby, the electron beam 50 is scanned on the sample 40 while vibrating in the X direction with a predetermined amplitude, vibration frequency, and phase defined by the output of the oscillation signal generator 75. And the voltage resulting from the absorption current which generate | occur | produces in the conductive pattern 40a which exists in the irradiation area | region of the electron beam 50 to be scanned is detected.

  By using such a scanning method of the electron beam 50 for the inspection apparatus 60 of the first embodiment, it is possible to grasp the presence or absence of a defect in the conductive pattern 40a or to specify a defective portion. According to such an inspection apparatus 60, it becomes possible to detect the defect of the conductive pattern 40a easily and with high accuracy. According to the inspection apparatus 60 of the first embodiment, at the development and manufacturing stage of a semiconductor device such as an LSI, defects are detected with high sensitivity, the cause of the defect is clarified, and the manufacturing process is optimized. High-performance and high-quality semiconductor devices can be manufactured.

Next, a second embodiment will be described.
FIG. 8 is a diagram illustrating a configuration example of the inspection apparatus according to the second embodiment. In FIG. 8, the same elements as those shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The inspection apparatus 80 of the second embodiment shown in FIG. 8 is the first implementation in that the absorption current generated in the conductive pattern 40a by the irradiation of the electron beam 50 onto the sample 40 is amplified by the differential current amplifier 81. This is different from the inspection device 60 in the form. The differential current amplifier 81 is electrically connected to a pair of probes 61a and 61b (or probes 61c and 61d).

  In the inspection apparatus 80 of the second embodiment, the scanning of the electron beam 50 can be performed in the same manner as in the case of the inspection apparatus 60 of the first embodiment. That is, using a scanning signal generation mechanism as shown in FIG. 4, a signal obtained by superimposing an oscillation signal (FIG. 7B) on an X-direction scanning signal (FIG. 7A) as shown in FIG. A Y-direction scanning signal as shown in FIG. 6 is input to the deflection electrode 62a and input to the deflection electrode 62c, and scanning is performed while the electron beam 50 is vibrated.

  When the specimen 40 is irradiated with the electron beam 50 by scanning in such a manner, an absorption current having a magnitude corresponding to the irradiation position of the electron beam 50 is generated. Then, for example, a signal of an absorption current that changes so as to vibrate according to the vibration of the irradiation position of the electron beam 50 is detected from the pair of probes 61a and 61b, and the current signal is amplified by the differential current amplifier 81 and amplified. The current signal (amplifier output) is input to the lock-in amplifier 64. In the lock-in amplifier 64, an amplifier output having the same frequency and phase as the oscillation signal is detected from the input amplifier output, and further, an amplifier output change amount during each oscillation when the electron beam 50 is scanned is detected. . The amplifier output and the amplifier output change detected by the lock-in amplifier 64 are output to the computer 65. The computer 65 arranges the amplifier output change using the scanning signal of the electron beam 50, and displays the image on the display device. 66.

  When there is a defect in the conductive pattern 40a of the sample 40, the amount of change in the amplifier output protrudes when the electron beam 50 is irradiated to the defective portion according to the example of FIG. Since an image of the display device 66 displays a bright spot or the like at a position corresponding to such a defective portion, the operator of the inspection apparatus 80 must grasp the presence or absence of a defect from the presence or absence of such a bright spot or the like. In addition, when there is such a bright spot, it is possible to specify a defective part from the position. Therefore, the defect of the conductive pattern 40a can be detected easily and with high accuracy.

  According to the inspection apparatus 80 of the second embodiment, defects are detected with high accuracy in the development and manufacturing stages of the semiconductor device, the cause of the defects is clarified, the manufacturing process is optimized, It becomes possible to manufacture a high-quality semiconductor device.

Next, a third embodiment will be described.
FIG. 9 is a diagram illustrating a configuration example of the inspection apparatus according to the third embodiment. In FIG. 9, the same elements as those shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The inspection apparatus 90 of the third embodiment shown in FIG. 9 determines the irradiation position of the electron beam 50 in addition to the deflection electrodes 62a and 62b for X-direction scanning and the deflection electrodes 62c and 62d for Y-direction scanning. The inspection apparatus 60 is different from the inspection apparatus 60 of the first embodiment in that it includes deflection electrodes 91a and 91b for vibrating in the X direction. Of the deflection electrodes 91a and 91b of the inspection apparatus 90, an oscillation signal (voltage signal) set to a predetermined amplitude, frequency, and phase is supplied to one deflection electrode 91a, for example, an amplifier (not shown). And the other deflection electrode 91b is grounded. A part of the oscillation signal is also input to the lock-in amplifier 64.

  In the inspection apparatus 90 of the third embodiment, an X-direction scanning signal as shown in FIGS. 5 and 7A is input to the deflection electrode 62a, and a Y-direction scanning signal as shown in FIG. By inputting to the deflection electrode 62c and inputting an oscillation signal as shown in FIG. 7B to the deflection electrode 91a, the electron beam 50 is scanned while oscillating at a predetermined amplitude, frequency and phase.

  By such scanning, as in the first embodiment, for example, a voltage signal due to an absorption current that changes so as to vibrate according to the vibration of the irradiation position of the electron beam 50 from the pair of probes 61a and 61b is generated. The detected voltage signal is amplified by the voltage amplifier 63, and the amplified voltage signal (amplifier output) is input to the lock-in amplifier 64. In the lock-in amplifier 64, an amplifier output having the same frequency and phase as the oscillation signal is detected from the input amplifier output, and further, an amplifier output change amount during each oscillation when the electron beam 50 is scanned is detected. . The amplifier output and the amplifier output change detected by the lock-in amplifier 64 are output to the computer 65. The computer 65 arranges the amplifier output change using the scanning signal of the electron beam 50, and displays the image on the display device. 66. Therefore, the defect of the conductive pattern 40a can be detected easily and with high accuracy.

  Such an inspection apparatus 90 according to the third embodiment also detects defects with high accuracy in the development and manufacturing stages of semiconductor devices, elucidates the cause of the defects, optimizes the manufacturing process, and provides high performance.・ High quality semiconductor devices can be manufactured.

  As in the third embodiment, in addition to the deflection electrodes 62a, 62b, 62c, and 62d for X-direction scanning and Y-direction scanning, deflection for vibrating the irradiation position of the electron beam 50 in the X direction. The configuration in which the electrodes 91a and 91b are provided can also be applied to the inspection apparatus 80 of the second embodiment using the differential current amplifier 81.

  In the first to third embodiments described above, the case where the X direction scanning signal, the Y direction scanning signal, and the oscillation signal for controlling the scanning of the electron beam 50 are all voltage signals has been described as an example. They can also be current signals. In that case, a current amplifier is used as the amplifying means.

  In the first to third embodiments described above, the change amount of the amplifier output of the voltage amplifier 63 or the differential current amplifier 81 during each vibration when the electron beam 50 is scanned while vibrating is a lock-in amplifier. 64. In addition, such an amplifier output change amount can be detected using the computer 65 without using the lock-in amplifier 64. In that case, for example, the lock-in amplifier 64 detects the amplifier output synchronized with the frequency and phase of the oscillation signal among the amplifier outputs of the voltage amplifier 63 or the differential current amplifier 81 and outputs it to the computer 65. . Then, the computer 65 uses the received amplifier output and executes a process of detecting the amount of change in the amplifier output during each vibration during the scanning of the electron beam 50 from the magnitude of the amplitude. Even with such a configuration, it becomes possible to detect the defect of the conductive pattern 40a easily and with high accuracy.

  In the first to third embodiments described above, the configuration considering the absorption current generated by the irradiation of the electron beam 50 and the noise when detecting the voltage caused by the absorption current has been described. It can also be set as the structure which does not. In this case, for example, the lock-in amplifier 64 is not used, and the amplifier output of the voltage amplifier 63 is input to the computer 65 without passing through the lock-in amplifier 64, and the change in the amplifier output is detected using the computer 65. You just have to do it. Alternatively, the lock-in amplifier 64 is used, but the lock-in amplifier 64 does not consider the frequency and phase during scanning of the electron beam 50, and detects only the amount of change in amplifier output and outputs it to the computer 65. May be.

  Moreover, the inspection apparatuses 60, 80, 90 of the first to third embodiments described above can be configured using an SEM. In that case, each inspection apparatus 60, 80, 90 detects secondary electrons generated from the sample 40 by irradiation of the electron beam 50 in addition to the function of acquiring and displaying the bright and dark image used for the defect inspection as described above. It also has a function of acquiring and displaying the surface image. In each of the inspection devices 60, 80, 90, for example, according to the scanning of the electron beam 50, the surface image of the sample 40 and the bright / dark image for defect inspection are appropriately switched and displayed on the display device 66, or these images are displayed side by side simultaneously. It is also possible to display on the device 66 or to superimpose these images and display them on the display device 66.

  In the first to third embodiments described above, the case where the operator finds a defective portion of the sample 40 from the image displayed on the display device 66 has been described as an example. Such processing is performed by the computer 65. Can also be done automatically. In this case, for example, the computer 65 performs a predetermined luminance adjustment on the image obtained from the amount of change in the amplifier output of the voltage amplifier 63 or the differential current amplifier 81, and there is a portion indicating a predetermined luminance difference in the image. Whether or not there is a defect in the irradiation region of the electron beam 50 on the sample 40 from which the image is obtained is determined from the presence or absence of a bright spot or the like in the image. If it is determined that there is a defect, the computer 65 causes the coordinates of the irradiation region of the electron beam 50 on the sample 40 from which the image is obtained, the bright spot in the image, etc. From the coordinates, the coordinates of the defective part on the sample 40 are acquired. Alternatively, without performing imaging of the amplifier output change amount of the voltage amplifier 63 or the differential current amplifier 81, the computer 65 is caused to directly execute the process corresponding to the above-described luminance adjustment with respect to the amplifier output change amount. It is also possible to execute the defect inspection process as described above using data.

  Further, the processing functions of the inspection apparatus used for defect inspection as exemplified above can be realized using a computer. In that case, a program describing the processing contents of the function that such an inspection apparatus should have is provided. By executing the program on the computer, a predetermined processing function is realized on the computer. The program describing the processing contents can be recorded in a computer-readable recording medium such as a magnetic recording device, an optical disk, a magneto-optical recording medium, a semiconductor memory, or the like. When distributing the program, for example, a portable recording medium on which the program is recorded is sold. It is also possible to store the program in a storage device of a server computer and transfer the program from the server computer to another computer via a network. The computer that executes the program stores, for example, the program recorded on the portable recording medium or the program transferred from the server computer in its own storage device. Then, the computer reads the program from its own storage device and executes processing according to the program. The computer can also read the program directly from the portable recording medium and execute processing according to the program. Further, each time the program is transferred from the server computer, the computer can sequentially execute processing according to the received program.

(Supplementary note 1) In an inspection apparatus for inspecting a sample,
Means for irradiating the sample with a charged beam;
Means for causing the charged beam to be irradiated to scan while vibrating the irradiation position with a constant amplitude;
Means for detecting an electrical signal generated in the sample by irradiation of the charged beam;
An inspection apparatus comprising:

  (Additional remark 2) It has a means to detect the variation | change_quantity of the said electrical signal detected between each vibration when scanning the said charged beam to irradiate, vibrating the irradiation position with fixed amplitude, It is characterized by the above-mentioned. The inspection apparatus according to appendix 1.

(Additional remark 3) It has a means to image the detected variation | change_quantity of the said electric signal, The inspection apparatus of Additional remark 2 characterized by the above-mentioned.
(Appendix 4) Means for scanning the charged beam to be irradiated while vibrating the irradiation position with a constant amplitude,
The inspection apparatus according to claim 1, wherein the charged beam is scanned while oscillating the irradiation position with a constant amplitude, frequency and phase.

  (Supplementary Note 5) Among the electric signals detected when the irradiation position of the charged beam is scanned while vibrating the irradiation position with a constant amplitude, frequency and phase, the same frequency as the vibration of the irradiation position of the charged beam is detected. The inspection apparatus according to claim 4, further comprising means for detecting an electrical signal having a phase.

  (Additional remark 6) The same frequency as the vibration of the irradiation position of the said charged beam detected during each vibration when scanning the said irradiation position while vibrating the irradiation position with a fixed amplitude, a vibration frequency, and a phase The inspection apparatus according to claim 5, further comprising means for detecting a change amount of the electrical signal of the phase.

(Supplementary note 7) The inspection apparatus according to supplementary note 6, further comprising means for imaging the detected change amount of the electrical signal having the same frequency and phase as the vibration of the irradiation position of the charged beam.
(Appendix 8) The sample has a conductive pattern,
The inspection apparatus according to claim 1, wherein the electrical signal is a voltage generated in the conductive pattern due to an absorption current generated in the conductive pattern by irradiation of the charged beam.

(Supplementary note 9) The sample has a conductive pattern,
The inspection apparatus according to claim 1, wherein the electrical signal is an absorption current generated in the conductive pattern by irradiation of the charged beam.

(Supplementary Note 10) In an inspection method for inspecting a sample,
An inspection method comprising: irradiating the sample with a charged beam while irradiating the irradiation position with a constant amplitude, and detecting an electric signal generated in the sample by the irradiation of the charged beam.

  (Additional remark 11) The amount of change of the said electric signal detected between each vibration when the charged beam to irradiate is scanned, vibrating the irradiation position with fixed amplitude is detected. Inspection method.

(Supplementary note 12) The inspection method according to supplementary note 11, wherein the detected change amount of the electrical signal is imaged.
(Supplementary note 13) When the sample is irradiated with the charged beam while scanning the irradiation position with a constant amplitude, the charged beam is vibrated with a fixed amplitude, frequency and phase. 11. The inspection method according to appendix 10, wherein the inspection is performed while scanning.

  (Supplementary Note 14) Of the electrical signals detected when the charged beam is scanned while vibrating its irradiation position with a constant amplitude, vibration frequency, and phase, the same frequency as the vibration of the charged beam irradiation position and 14. The inspection method according to appendix 13, wherein a phase electrical signal is detected.

  (Supplementary Note 15) The same frequency as the vibration of the charged beam irradiation position detected during each vibration when the charged beam is scanned while vibrating the irradiation position with a constant amplitude, vibration frequency and phase, 15. The inspection method according to appendix 14, wherein a change amount of the electrical signal of the phase is detected.

(Supplementary note 16) The inspection method according to supplementary note 15, wherein the detected change amount of the electrical signal having the same frequency and phase as the vibration of the irradiation position of the charged beam is imaged.
(Supplementary note 17) The inspection method according to supplementary note 10, wherein the electrical signal is a voltage generated in the conductive pattern by an absorption current generated in the conductive pattern of the sample by irradiation of the charged beam.

  (Supplementary note 18) The inspection method according to supplementary note 10, wherein the electrical signal is an absorption current generated in a conductive pattern of the sample by irradiation of the charged beam.

It is explanatory drawing of a test | inspection principle, (A) is a figure which shows the mode of electron beam irradiation to a conductive pattern typically, (B) is a model showing the relationship between the electron beam irradiation position of a conductive pattern, and amplifier output variation | change_quantity. FIG. It is explanatory drawing at the time of scanning without vibrating an electron beam, (A) is a figure which shows the mode of electron beam irradiation to a conductive pattern typically, (B) is the electron beam irradiation position and amplifier of a conductive pattern It is a figure which shows the relationship with an output typically. It is a figure which shows the structural example of the test | inspection apparatus of 1st Embodiment. It is a figure which shows the structural example of a scanning signal production | generation mechanism. It is a figure which shows the example of an output of a X direction scanning signal production | generation part. It is a figure which shows the example of an output of a Y direction scanning signal production | generation part. It is a figure which shows together the example of an output of a X direction scanning signal generation part and an oscillation signal generation part, Comprising: (A) is an example of an output of an X direction scanning signal generation part, (B) is an example of an output of an oscillation signal generation part. . It is a figure which shows the structural example of the test | inspection apparatus of 2nd Embodiment. It is a figure which shows the structural example of the test | inspection apparatus of 3rd Embodiment.

Explanation of symbols

10, 40a Conductive pattern 11 Wiring 12, 12a Via 20, 50 Electron beam 31, 32, 61a, 61b, 61c, 61d Probe 40 Sample 60, 80, 90 Inspection device 61 Sample chamber 61e Stage 62 Electron beam irradiation unit 62a, 62b , 62c, 62d, 91a, 91b Deflection electrodes 62e, 62f Lens 63, 72, 74 Voltage amplifier 64 Lock-in amplifier 65 Computer 66 Display device 71 X-direction scanning signal generation unit 73 Y-direction scanning signal generation unit 75 Oscillation signal generation unit 81 Differential current amplifier

Claims (6)

In the inspection device that inspects the sample,
Means for irradiating the sample with a charged beam;
Means for causing the charged beam to be irradiated to scan while vibrating the irradiation position with a constant amplitude;
Means for detecting an electrical signal generated in the sample by irradiation of the charged beam;
An inspection apparatus comprising:   2. The apparatus according to claim 1, further comprising means for detecting a change amount of the electric signal detected during each vibration when the irradiation beam is scanned while vibrating the irradiation position with a constant amplitude. The inspection device described.   3. The inspection apparatus according to claim 2, further comprising means for imaging the detected change amount of the electric signal. In an inspection method for inspecting a sample,
An inspection method, comprising: irradiating the sample with a charged beam while oscillating the irradiation position with a constant amplitude; and detecting an electric signal generated in the sample by the irradiation of the charged beam.   5. The inspection method according to claim 4, wherein a change amount of the electric signal detected during each oscillation when the irradiation beam is scanned while oscillating the irradiation position with a constant amplitude is detected. .   6. The inspection method according to claim 5, wherein the detected change amount of the electrical signal is imaged.

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